Lateral Extra-articular Tenodesis Restores Knee Rotational and Translational Stability Regardless of Fixation Type: A Matched-Pair Cadaveric Study.

BACKGROUND

Lateral extra-articular tenodesis (LET) is used as an adjunct to anterior cruciate ligament reconstruction (ACLR) to enhance stability. However, understanding of the optimal fixation method is limited.

PURPOSE/HYPOTHESIS: The purpose was to compare biomechanical knee stability using 3 femoral LET fixation methods before and after cyclic loading. It was hypothesized that the fixation achieved with a suture anchor or an interference screw would demonstrate greater stability than that achieved with a metallic staple.

STUDY

DESIGN

Controlled laboratory study.

METHODS

Ten matched pairs of cadaveric knees (mean age 64 years) underwent modified Lemaire LET. Each pair received suture anchor fixation on 1 knee and either interference screw (arm A) or metallic staple (arm B) fixation on the contralateral knee. Specimens were tested in 4 states: intact (native), anterolateral knee lesion, modified Lemaire (LET) procedure, and modified Lemaire (LET) procedure after cyclic loading. Cyclic loading consisted of 2000 cycles of 5 N·m internal rotation at 1 Hz. Anterior translation was applied at 90 N of force using visual marker motion capture. Internal rotation was measured using a 5 N·m moment and a digital inclinometer.

RESULTS

No significant differences in anterior translation were observed between the different states (anterolateral lesion, LET, and post-cyclic loading) for all constructs. The mean increase in internal rotation among the subgroups after undergoing anterolateral lesion ranged from 2.1° to 4.0°. No significant difference was found in mean internal rotation after samples underwent cyclic loading in both arms of the study (arm A [suture anchor vs screw], P = .262; arm B [suture anchor vs staple], P = .450). Specimen undergoing suture anchor fixation demonstrated significantly greater change in internal rotation from pre- to post-cyclic loading than those using screw fixation (arm A, 7.2% ± 2.3% vs -1.3% ± 2.6%, respectively; P = .011) but not staple fixation (arm B, 14.3% ± 16.7% vs 5.3% ± 3.1%; P = .338). Internal rotatory stability was restored by all LET methods even after undergoing cyclic loading.

CONCLUSION

All fixation methods restored rotational stability to near-native levels even after loading. Suture anchor fixation appeared more vulnerable to cyclic loading than the other 2 methods.

CLINICAL RELEVANCE: Suture anchors appeared most vulnerable to cyclic loading. No significant difference was found in absolute mean internal rotation values between suture anchors and screws or staples. Clinically, all 3 methods remain viable options for LET fixation. Staples and screw may better resist cyclic physiologic stress when compared with suture in controlled settings; however, this may not be clinically significant.